Films in OLED (organic electroluminescent display) are primarily formed by an evaporation process or a solution process. The evaporation process has been widely applied to small size devices, and currently has been applied in mass production. In case of being applied to large scale devices, the evaporation process suffers from great defects. For example, a light shielding plate tends to displace in the high temperature environment of the process, making it difficult to obtain a uniform rate of deposition on a base plate. The solution process primarily comprises ink jet printing, nozzle coating, spin coating, screen printing or the like. In the ink jet printing, a uniform film can be deposited by spraying liquid-state organic material, the utilization rate of material is high, and it is easy to realize large size device. Thus, the ink jet printing is considered as an important approach for mass production of a large size OLED.
However, the ink jet printing belongs to a continuous printing, and it is necessary to continuously spray liquid on the base plate. In this way, during printing as shown by a side view of an existing OLED device in FIG. 1, the liquid can be sprayed onto an excepted region apart from an active region (AA region), such as a spare region and a contact hole region. After printing, an additional process is required to clean up the liquid in the excepted region, to prevent the residual liquid from damaging the OLED device and thus leading to display defects. Currently, plasma dry etching, laser cleaning, or side-wiping is used to clean the residual liquid in the excepted region. These cleaning methods usually can not clean up a region with micro-patterns in the excepted region. For example, if there is residual liquid in a through hole in the contact hole region, it is difficult to clean up the residual liquid. However, the residual liquid in the through hole tends to lead to display defects.
Therefore, it is urgent for a skilled in the art to effectively prevent liquid from being residual in a region with micro-pattern in the excepted region.